UNIVERSITI PUTRA MALAYSIA

IMPROVEMENTS IN DESIGN OF LOCAL FLUORESCENT ELECTRONIC BALLASTS IN COMPLIANCE WITH THE RELATED

LOCAL AND INTERNATIONAL STANDARDS

ZULKEFLI BIN YAACOB

FK 2001 61

IMPROVEMENTS IN DESIGN OF LOCAL FLUORESCENT ELECTRONIC BALLASTS IN COMPLIANCE WITH THE RELATED

LOCAL AND INTERNATIONAL STANDARDS

By

ZULKEFLI BIN Y AACOB

Thesis Submitted in Fulfilment of the Requirement for the Degree of Master of Science in the Faculty of Engineering

Universiti Putra Malaysia

February 2001

Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfilment of the requirement of the degree of Master of Science.

IMPROVEMENTS IN DESIGN OF LOCAL FLUORESCENT ELECTRONIC BALLASTS IN COMPLIANCE WITH THE RELATED

LOCAL AND INTERNATIONAL STANDARDS

By

ZULKEFLI BIN Y AACOB

February 2001

Chairman: Ir. Dr. Md. Yusof Ismail

FaCUlty: Engineering

The fluorescent electronic ballast has been in the market for a long time but has not

created any great impact in the illumination industry due to its high initial cost of

investment compared to the conventional magnetic ballast. With the advancement

in power electronics and utilization of power semiconductor which is available

commercially today, it is now possible to implement almost every type of desired

conversion of current, voltage or frequency and availability of electronic

components with higher power ratings. Thus, it is now possible to manufacture an

economically priced, light weight, lower watt-loss and high quality with maximum

performance electronic ballast which is compatible with all types of fluorescent

luminaries.

11

This study is undertaken to improve the design of existing locally manufactured

electronic ballasts. The study indicated that many of these commercial electronic

ballasts only have partial or minimum compliance requirements or none at all to the

related local and international standards, namely MS IEC 928, MS IEC 929 and

EMC requirements as stipulated by SIRIM Berhad. From a survey on nine

different ballast manufacturers, only seven manufacturers conducted two tests on

MS IEC 928 and MS IEC 929 and only two manufacturers conducted a complete

list of tests to ascertain whether their product comply with the related local and

international standards. Since electronic ballast is listed as one of the electrical

controlled items by the Department of Electricity and Gas Supply of Malaysia

(DEGSM), it is crucial that the EMC test be imposed prior to ballast approval.

A directive was issued by the Malaysian government on the 3rd of July 1998 to

implement energy conservation and to promote the use of energy efficient

equipment specifically on lighting luminaries and lighting control systems.

DEGSM noted the limitations of fluorescent ballast watt-loss hence, this study is

undertaken to meet the implementation of energy conservation regulations/act in

the near future.

The study discussed the advantages and disadvantages of electronic ballasts, their

operation and performance characteristics and problems encountered during their

normal operations, for instance, surges, starting current, power factor, watt-loss.

11l

ambient temperature and environmental effects, lamp/ballast premature failures,

harmonics and electromagnetic (EM) disturbances, efficiency and dimming.

VariOllS samples of electronic ballast were collected and tested for compliances

with local and international standards. It was found that many samples failed the

tests on total harmonic distortion (THD) which exceeded the 25% limit.

From the test data collected on the study, the findings from the analysis on the

operation, performance, design and construction of the typical electronic ballast

were utilised in the construction of two improved versions of electronic ballast

prototypes. The two improved versions were retested and both passed all the tests

conducted on them with better results.

I\"

Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi keperluan untuk ijazah Master Sains.

PEMBAIKAN DALAM REKA BENTUK BALLAST ELEKTRONIK PENDAFLUOR TEMPATAN DI DALAM MEMENUHI PIA W AI-PIA W AI

TEMPATAN DAN ANTARABANGSA YANG BERKAITAN

Oleh

ZULKEFLI BIN Y AACOB

Februari 2001

Pengerusi: Ir. Dr. Md. Yusof Ismail

Fakulti: Kejuruteraan

Ballast elektronik bagi kelengkapan lampu pendafluor telah lama berada di dalam

pasaran tetapi tidak dapat memberi sebarang impak yang ketara di dalam industri

pencahayaan disebabkan oleh kos pelaburan awal yang agak tinggi jika

dibandingkan dengan ballast konvensional jenis magnetik. Dengan kemajuan di

dalam bidang elektronik kuasa dan penggunaan semikonduktor kuasa secara

kommersil yang terdapat sekarang ini, ianya berupaya untuk melaksanakan hampir

setiap jenis penukaran yang diinginkan bagi arus, voltan atau frekuensi dan

kedapatannya komponen-komponen elektronik yang berkadaran kuasa tinggi.

Maka dengan itu, buat masa ini, adalah berkemungkinan besar untuk menghasilkan

ballast elektronik pada kos yang lebih ekonomik, ring an, berkehilangan watt rendah

dan berkualiti tinggi pada pedaksanaan yang maksima bersesuaian dengan semua

jenis kelengkapan lampu pendafluor.

v

Kajian ini adalah bertujuan untuk memperbaiki reka bentuk bagi ballast elektronik

buatan tempatan sedia ada. Kajian menunjukkan bahawa kebanyakan ballast

elektronik kommersil tidak mempunyai, hanya mempunyai sebahagian atau

pematuhan minima ke atas keperluan berdasarkan piawai-piawai tempatan dan

antarabangsa berkaitan saperti MS IEC 928, MS lEC 929 dan keperluan bagi

kesesuaian elektromagnetik (EMC) sapertimana yang diperlukan oleh SIRIM

Berhad. Daripada kajian yang telah dibuat ke atas 17 contoh yang dikumpulkan

daripada sembilan pengeluar ballast elektronik yang berlainan, hanya tujuh

pengeluar telah melakukan dua ujian bagi MS IEC 928 dan MS IEC 929 dan hanya

dua pengeluar sahaja telah melakukan senarai lengkap ujian. Ini adalah penting

kerana ballast elektronik adalah merupakan salah satu daripada barangan e1ektrik

terkawal oleh Jabatan Bekalan Elektrik dan Gas Malaysia (JBEGM).

Kajian ini juga membincangkan tentang kebaikan dan keburukan tentang ballast

elektronik, ciri-ciri operasi dan perlaksanaan dan juga masalah-masalah yang

dihadapi semasa ianya beroperasi secara normal saperti penerpaan, arus mula,

faktor kuasa, kehilangan watt, suhu sekeliling dan kesan keatas alam sekitar,

kegagalan pra-matang bagi lampulballast, harmonik dan kesan gangguan

elektromagnetik (EM), kecekapan dan pemalapan.

Pelbagai contoh ballast elektronik telah dikumpulkan dan diuji-kaji bagi

memastikan pematuhan berdasarkan kepada keperluan dan telah didapati bahawa

kebanyakan contoh yang diuji telah gagal bagi ujian "Jumlah Herotan Harmonik"

vi

yang mana melebihi tahap 25%. Daripada data ujian yang dikumpulkan di atas

kajian yang telah dibuat, analisa ke atas operasi, perlaksanaan, reka bentuk dan

pembinaan bagi ballast biasa telah digunakan di dalarn pembinaan dua versi contoh

sulung ballast elektronik yang telah diperbaiki. Ianya telah diuji sebagaimana yang

telah dilakukan keatas contoh-contoh yang telah dikumpulkan di mana kedua­

duanya telah didapati lulus kesemua ujian berkenaan dengan contoh sulung yang

kedua telah memberikan keputusan yang lebih baik.

Pada bahagian akhir kajian, data-data telah terkumpul telah dijadualkan untuk

perbincangan dan perbandingan secara keseluruhan dalarn menentukan sarna ada

contoh-contoh dan contoh sulung tersebut telah dapat memenuhi keperluan piawai­

piawai berkenaan secara sepenuhnya atau tidak. Kesimpulan ke atas kaj ian

kemudiannya telah dibuat. Penyelidikan lanjut dan perakuan telah dicadangkan

berdasarkan kepada pendekatan reka bentuk bam, topologi-topologi dan teknik­

teknik bagi pembinaan ballast elektronik dengan merujuk kepada penyelidikan

yang dijalankan oleh berbagai pereka ballast elektronik.

Vll

ACKNOWLEDGEMENTS

A great effort went into the writing-up of this thesis which has been a great

experience and an enrichment of knowledge. I would like to thank the following

people and organisations for their contributions, without which this thesis could

never have been completed.

First and always, my family. My ever-patient and supportive wife and two

daughters, who have made many sacrifices during the duration and understood my

need to further my studies. Thank you for your sincere emotional support, patience

and understanding.

Thank you also to Ir. Dr. Md. Yusof Ismail, my supervisor and co-supervisors, Ir.

Dr. Norman Mariun, Dr. Megat Hamdan Megat Ahmad and Dr. Mohd. Sapuan

Salit for their tireless effort, guidance and generous recommendations and insights

throughout the process of the writing-up of the thesis.

Thank you also to the electronic ballast manufacturers for their cooperation in

allowing me to utilise their available technical resources and testing facilities

during the research and for the analysis conducted on the thesis.

Vlll

I certify that an Examination Committee met on 6th Februari 2001 to conduct the final examination of Zulkefli Yaacob on his Master of Science thesis entitled "Improvements in Design of Local Fluorescent Electronic Ballasts in Compliance with Related Local and International Standards" in accordance with the Universiti Pertanian Malaysia (higher Degree) Act 1980 and Universiti Pertanian Malaysia (Higher Degree) Regulations 1981. The Committee recommends that the candidate be awarded the relevant degree. Members of the Examination Committee are as follows:

SHAMSUDDIN SULAIMAN, Ph. D., Associate Professor, Faculty of Engineering Universiti Putra Malaysia (Chairman)

MD.YUSOF ISMAIL , Ph. D., P.Eng., Associate Professor, Faculty of Engineering Universiti Putra Malaysia (Member)

NORMAN MARIUN, Ph. D., P.Eng., Associate Professor, Faculty of Engineering Universiti Putra Malaysia (Member)

MEGAT MOHAMAD HAMDAN MEGAT AHMAD, Ph. D., Faculty of Engineering Universiti Putra Malaysia (Member)

MOHD. SAPUAN SALIT, Ph. D., Faculty of Engineering Universiti Putra Malaysia (Member)

Q �-----------------------------

MOH . G MALI MOHA YIDIN, Ph. D., ProfessoilDeputy Dean of Graduate School, Universiti Putra Malaysia.

Date:

IX

This thesis submitted to the Senate of Universiti Putra Malaysia was accepted as fulfilment of the requirement for the degree of Master of Science.

x

HAZALI MOHA YIDIN, Ph.D.

Professor Deputy Dean of Graduate School Universiti Putra Malaysia

Date:

DECLARATION

I hereby declare that the thesis is based on my original work except for quotations and citations which have been duly acknowledged. I also declare that it has not been previously or concurrently submitted for any other degree at UPM or other institutions.

Xl

Name: ZULKEFLI BIN Y AACOB

Date: 1. fl/ '2{ too I

TABLE OF CONTENTS

Page ABSTRACT 11 ABSTRAK v ACKNOWLEDGEMENTS Vlll APPROVAL SHEET ix DECLARATION Xl LIST OF TABLES XIV LIST OF FIGURES xv LIST OF ABBREVIATIONS XIX GLOSSARY OF TERMS XXll

CHAPTER

I INTRODUCTION 1 . 1 Energy Consumption in Malaysia 1 1 .2 Test Standards Practices by Other Countries 8 1 .3 Recent Energy Efficiency Programs and

Activities in Malaysia 8 1.4 Energy Using Products 1 1 1.5 Fluorescent Ballasts 1 2 1 .6 Energy Efficient Lighting and Lighting

Controls Strategies 1 4 1 .7 Energy Conservation and Management 1 5 1 .8 Objectives of the Study 1 8

II LITERATURE REVIEW 2.1 Fluorescent Luminaries 1 9

2. 1 . 1 Fluorescent Lamps 1 9 2. 1.2 Power Factor Capacitor 23 2. 1 .3 Glow Starter 24 2. 1.4 Fluorescent Ballasts 25

2.2 Factors Effecting Performance of Fluorescent Luminaries 31

2.3 Testing of Electronic Ballasts by SIRlM Berhad 33 2.4 Advantages and Disadvantages of Electronic

Ballasts for Fluorescent Lamps 35 2.5 Harmonic and its Impact on Electrical Safety 37 2.6 Electromagnetic Compatibility (EMC) 41 2.7 Effects of Electronic Ballast Operation and performance

to Envirorunent and on Utility Voltage Stability 42 2.8 Electromagnetic Interference (EMI) from High

Frequency Ballasts 46

XII

2.9 Overview on the Principles of Electronic Ballasts for Fluorescent Lamps. 50

2.10 Principles of Electronic Ballast Circuit Design 51 2.10.1 Two-Stage Electronic Ballasts 52 2.1 0.2 Single-Stage Electronic Ballasts 53

III METHODOLOGY 3.1 Introduction 64 3.2 Preliminary Design Approach 65

3.2.1 Model Implementation in Circuit Simulators 66 3.2.2 Fluorescent Lamps 67 3 .2.3 Electronic Ballast 8 1

IV DESIGN AND CONSTRUCTION 4. 1 Typical Electronic Ballast Design 84 4.2 Analysis, Design and Experiment of High-Power

Factor Electronic Ballast 86 4.3 Steady State Analysis and Design Issues 96 4.4 Lamp Power Control 1 06 4.5 Simulation and Experimental Results 108 4.6 Efficiency Improvement of Electronic Ballast 1 12 4.7 Design and Analysis of Dimming Electronic Ballast 1 17

V RESULTS AND DISCUSSION 5.1 Introduction 124 5.2 Test Standards and Procedures 1 25 5.3 Design and Construction of Electronic Ballast

Prototypes 126 5.4 Test Results on Electronic Ballast Testing 127 5.5 Discussion on Results 1 32 5 .6 Summary of the Study 136 5.7 Research Findings and Discussion 138

VI CONCLUSION AND RECOMMENDATIONS 6.1 Introduction 141 6.2 Conclusion 1 42 6.3 Recommendations and Further Works 1 44

REFERENCES 149 APPENDICES

A 155 B 167

BIODATA OF AUTHOR 223

xiii

LIST OF TABLES

Table Page

1 .1 Statistics of main utilities and licensees 7

1 .2 Electrical power consumption on Peninsular Malaysia 7

1 .3 Maximum allowable watt-loss for fluorescent ballasts by DEGSM 12

1 .4 Minimum allowable coefficient of performance (COP) for electric fans by DEGSM 1 3

2.1 Multiplication factors for fluorescent lamp burning hours 22

2.2 Fluorescent ballast sound ratings 33

2.3 Variations of the voltage control charge pump 58

3 . 1 The V-I characteristics of Os ram FO 321741 18 instant start fluorescent lamp 70

3 .2 Simulation and measurement results of the lamp 74

3.3 Experimental results on efficiency improvement of electronic ballast 1 1 7

4.1 Comp�son of the test results between selected ballast samples and prototypes 1 34

5.l Comparison of the test results between selected 2 X 36 W electronic ballast samples and prototypes 1 51

XIV

LIST OF FIGURES

Figure Page

2 . 1 Fluorescent Lamp 21

2.2 Energy Distribution for Fluorescent Lamp 22

2.3 Waveform Distortion Due to Harmonic Effects 3 8

2.4 General Fluorescent Lamp Characteristic 50

2.5 Block Diagram of an Electronic Ballast 5 1

2.6 Two·stage Electronic Ballast 53

2.7 Half·bridge with One Integrated Boost Converter 54

2.8 Half-bridge with Two Integrated Boost Converters 55

2.9 Mains Current without EMC Filter and DC Link Voltage of an Electronic Ballast with Boost Converter at 230 Vac 55

2. 1 0 Half·bridge with One Integrated Buck Boost Converter 56

2 . 1 1 Half-bridge with Two Integrated Buck Boost Converters 57

2. 12 Half·bridge with Voltage Controlled Charge Pump 57

2.1 3 Mains Current from a Voltage Controlled Charge Pump Circuit 59

2. 14 Half·bridge with Combined CurrentIV oltage Charge Pump 59

2. 1 5 Improved Charge Pump Topology 60

2.1 6 Charge Pump with Additional Inductor 6 1

2. 1 7 Improved Charge Pump with Additional Inductor 62

2.18 Another Current Controlled Charge Pump 63

3 . 1 A Measurement Circuit of Fluorescent Lamp 69

xv

3.2 V-I Characteristics Plot of Os ram FO 32W1741 TS Instant Start Fluorescent Lamp 70

3.3 The Proposed PSpice Circuit for the Lamp Model 73

3.4 A Circuit for Testing the Proposed Lamp Model 73

3.S(a) The Negative Dynamic Resistance Characteristics of the Lamp Obtained from Simulation 75

3.5(b) The Negative Dynamic Resistance Characteristics of the Lamp Obtained from Experiment 75

3.6 A Simplified Schematic of the Half-bridge Resonant Ballast 76

3.7 The Plot of the Normalised Current Versus Operating Frequency with Various Zo(o) and V H(o) as Parameters 78

3.S(a), (c) The Simulation Results of the System 80

3.8(b), (d) The Experimental Results of the System 80

3.9 The Typical Ballast Circuit 82

3.10 Comparison of Power Input 83

3.11 Comparison of Light Output 83

4.1 The PF Correction Converter Block Diagram 88

4.2 The Required Output Characteristics of Box to Achieve PF Correction 88

4.3 High Power Factor ACIDC Converter 89

4.4 Characteristics of a Series Resonance Converter 89

4.5 High PF Correction ACIDC Converter 90

4.6 The Basic Charge Pump PF Correction ACIDC Converter 90

4.7 VS-CPPFC Electronic Ballast 91

XVI

4.8 The Simplified VS-CPPFC Converter 91

4.9 Switched Waveform of Figure 3.19 92

4.10 CPPFC Electronic Ballast 96

4.11 Equivalent Circuit of Figure 3.21 97

4.12 Eight Topological Stages 98

4.13 Key Waveforms of the Electronic Ballast 99

4.14 Symmetrical CPPFC Electronic Ballast 105

4.15 The Lamp Power Control Diagram 108

4.16 DC Bus Voltage Across the Bulk Capacitor, CB During Preheat and Start-up Modes 109

4.17 The Simulated Switching Waveforms 110

4.18 The Experimental Switching Waveforms 110

4.19 The Measured Input Line Current Waveforms 111

4.20 The Measured Switching Waveforms of the Symmetrical CPPFC Electronic Ballast 111

4.21 Half-bridge Inverter Circuit Configuration 113

4.22 The Block Diagram of the Improved Efficiency Electronic Ballast 116

4.23 The Power Circuit for Dimming Electronic Ballast 119

4.24 Half-bridge Inverter Output Waveforms at 0)5>(00 120

5 .1 The Block Diagram of Electronic Ballast Prototype No.1 127

5.2 The Block Diagram of Electronic Ballast Prototype No.2 127

XVll

5.3 The Schematic Diagram of Electronic Ballast Prototype No.1 128

5.4 The Schematic Diagram of Electronic Ballast Prototype No. 2 129

5.5 Photograph of Electronic Ballast Prototype No. 1 130

5.6 Photograph of Electronic Ballast Prototype No. 2 130

6.l CIC-CPPFC Conceptual Circuit 145

6.2 CIC-CPPFC Electronic Ballast 145

6.3 CIC-CPPFC Converter Diagram and its Waveforms 146

XVlll

LIST OF ABBREVIATIONS

AC

ANN ANSI

BSI

CBM

CCF

CENELEC

CFL

CIC

CISPR

CO

CO2

COP

CPPFC

CS

dB

DC

DCM

DEGSM

DSM

ECM

EEO

EM

EMC

EMF

EMI

ESD

ESR

EUT

Alternating Current

Artificial Neural Network

American National Standards Institute

British Standard Institute

Certified Ballast Manufacturers Association

Current Crest Factor

European Committee for Electrotechnical Standardisation

Compact Fluorescent Lamp

Continuous Input Current

International Special Committee on Radio Interference

Carbon Monoxide

Carbon Dioxide

Coefficient of Performance

Charge Pump Power Factor Correction

Current Source

Decibles

Direct Current

Discontinuous Current Mode

The Department of Electricity and Gas Supply of Malaysia

Demand Side Management

Energy Centre of Malaysia (pusat Tenaga Malaysia)

Energy Efficiency Officer

Electromagnetic

Electromagnetic Compatibility

Electromotive Force

Electromagnetic Interference

Electrostatic Discharge

Equivalent Series Resistance

Equipment Under Test

xix

FCC

FLEB

GDP

GTO

HVAC

HF

HID HPS

HVDC

IC

IEC

IEEE

IES

IGBT

IPP

ISO

KPBE

LISN

LLS

LPW

MOSFET

MS

NEC

NEMA

NLPIP

NTC

PCB

PF

PFC

PLC

Federal Communications Commission

Fluorescent Lamp with Electronic Ballast

Gross Domestic Product

Gate Turn-off

Heating, Ventilating and Air-conditioning

High Frequency

High Intensity Discharge

High Pressure Sodium

High Voltage Direct Current

Integrated Circuit

International Electrotechnical Commission

Institution of Electrical and Electronics Engineers

llluminating Engineers Society

Insulated Gate Bipolar Transistor

Independent Power Producer

International Organisation for Standardisation

Ketua Pengarah Bekalan Elektrik (Director General of Electricity

Supply)

Line Impedance Simulation Network

Lembaga Letrik Sabah (Sabah Electricity Board)

Lumen per Watt

Metal Oxide Semiconductor Field Effect Transistor

Malaysian Standard

National Electrical Code

National Electrical Manufacturers Association

National Lighting Product Information Program

Negative Temperature Coefficient

Printed Circuit Board

Power Factor

Power Factor Correction

Power Line Carrier

xx

PSpice

PWD

PWM

RCCB

RF

RFI

RLO

RMS

SCR

SESCO

SIRIM

S02

SPICE

SLICE

THD

TNB UDCS

UL

UPS

US FDA

UVLO

VCO

VDC

VS

A member of SPICE family of Circuit Simulators

Public Works Department

Pulse Width Modulation

Residual Current Circuit Breaker

Radio Frequency

Radio Frequency Interference

Relative Light Output

Root Mean Square

Silicon Control Rectifier

Sarawak Electricity Supply Corporation

Standards and Industrial Research Institute of Malaysia

Sulphur Dioxide

Simulation Program with Integrated Circuit Emphasis

Circuit simulator program developed by Harris Semiconductor

Total Harmonic Distortion

Tenaga Nasional Berhad

User Defined Controlled Source

Underwriters Laboratories of USA

Uninterruptible Power Supply

Food and Drug Administration of USA

Under-voltage Lockout

Voltage Cut-out

DC Voltage Source

Voltage Source

xxi

GLOSSARY OF TERMS

The following technical and lighting terminologies are frequently used with reference to the study. These are presented in alphabetical order and explained so that they are easy to understand. For a complete range of lighting terminology and precise defInitions, please refer to the IES Lighting Handbook, 1981.

Active Filter

Advance, Firing Angle

Ambient temperature

Asymmetrical

Avalanche

Avalanche Diode

A filter which is switched in response to demand to

attenuate or eliminate harmonic components and

compensate for active power.

The angle at which a thyristor starts conduction in

advance of, and relative to, the instant when the

thyristor forward voltage falls to zero in a converter.

Used in relation to the inverting mode of operation.

The temperature of the general mass of air or cooling

medium into which heat is finally transferred from a

hot body.

Not uniform in characteristic or construction.

A chain reaction which occurs when minority carriers

are accelerated by a high electric field, so liberating

further carriers leading to a sharp increase in reverse

current and breakdown.

A diode which may temporarily be exposed to

voltages of the order of the breakdown voltage.

XXll

Ballast

Ballast Factor

Bidirectional

Breakdown Voltage

Bridge

Chopping

Clamping Voltage

Closed-loop

Colour Rendering

Commutating Diode

A device used with gaseous discharge lamps that

provides necessary conditions to start and operate the

lamps.

The percentage of light produced by a commercial

ballast compared to a reference or standard ballast.

Capable of current conduction in both directions, for

example a triac.

The reverse voltage level at which the reverse current

increases rapidly in a diode.

Full-wave converter.

A technique of rapidly switching on and off a source

of voltage.

Introduction of a voltage reference level to a pulsed

or transient waveform to limit the peak value.

A system in which information regarding the state of

a controlled quantity is fed back to the controlling

element.

An expression for the effect of a light source on the

colour appearance of objects in comparison with their

colour appearance under a reference light source.

A diode placed across a DC load to permit transfer of

load current away from the source, and so allow the

xxiii

Conducting Angle

Conduction Loss

Constant-current Inverter

Constant-voltage Inverter

Converter

Critical Damping

Damping

D.C Link

Delay, Firing Angle

thyristors in the DC source to turn off. In addition to

permitting commutation of the source thyristors, the

diode will prevent reversal of the load voltage.

The angle over which a device conducts.

The energy dissipated within the device during the

on-state conduction.

An inverter fed from a DC source with a large series

inductor, so that over each inverter cycle the source

current remains almost constant.

An inverter fed from a DC source with a large

parallel capacitor, so that over each inverter cycle the

source voltage remains almost constant.

A circuit which convert AC to DC or vise versa.

Damping which gives most rapid transient response

without overshoot or oscillation.

Extraction of energy from an oscillating system.

Intermediate DC stage between two systems of

different frequency.

The retarded angle at which a thyristor starts

conducting relative to that instant when the thyristor

xxiv